A database is a collection of data that is organized to facilitate access and updates to the data. Databases can be categorized according to the type of data they contain, such as bibliographic, numeric, textual, image, transactional, or other data, for example. Databases can also be categorized according to the organizational approach used, such as relational, hierarchical, object-oriented, and hybrid approaches, for example.
Databases are sometimes instantiated for use in different contexts, such as a development context in which new functionality is created, a pre-production context in which new functionality is tested before the database is released to production, and a production context in which the database stores live data and is commercially relied upon, for example. Databases may also be instantiated multiple times on multiple servers within a given context, to provide faster access and reliability through redundancy. A given database instance may include database management software, tables and other data-containing structures, indexes into the data, data access and/or manipulation procedures, memory resources, and other items. A database instance is sometimes called a database environment.